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Nitrous oxide (N2O) emissions from agriculture can be tackled by reducing demand for, and consumption of, nitrogen (N) inputs via diet modification and waste reduction, and/or through technologies applied at the field level. Here we focus on the latter options. Opportunities for mitigating N2O emissions at the field level can be advanced by a clearer scientific understanding of the system complexities leading to emissions, while maintaining agricultural system sustainability and productivity. A range of technologies are available to reduce emissions, but rather than focus specifically on emissions, the broader management and policy focus should be on improved N use efficiency and effectiveness; for lower N2O emissions per unit of crop and animal product, or per unit of land area.
This work was supported by UK NERC: ADVENT (NE/1806209), ADVANCES, FAB-GGR (NE/P019951/1) and UBERC Phase 4 project funding
Expandable Liner Hanger Application in Arduous Well Conditions Proves Reliability: A Case History Joseph Cantu; Joseph Cantu Anadarko Petroleum Corp. Search for other works by this author on: This Site Google Scholar Pete Smith; Pete Smith Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar Ron Nida Ron Nida Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, October 2004. Paper Number: SPE-88510-MS https://doi.org/10.2118/88510-MS Published: October 18 2004 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Cantu, Joseph, Smith, Pete, and Ron Nida. "Expandable Liner Hanger Application in Arduous Well Conditions Proves Reliability: A Case History." Paper presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, October 2004. doi: https://doi.org/10.2118/88510-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Asia Pacific Oil and Gas Conference and Exhibition Search Advanced Search ProposalIn an effort to increase production in the gas fields of East Texas, horizontal wells have become the standard, as they have in many regions worldwide. Many times the horizontal section is preceded with a drilling liner to cover the build section of the well and isolate weaker fracture gradient zones prior to penetrating the production interval. Previously, many operational challenges were encountered during liner installation, resulting in costly shoe and liner top remedial operations or the inability to reach the total depth of a hole section. Primary among the hurdles are successfully deploying the liner across the weaker zones and negotiating the hole angle.With the recent advancements made in the field of solid expandable tubular technology, several innovative products have developed from the core technology. One of these products is the expandable liner hanger. This product has been proven to greatly enhance liner operations in the well construction industry.Expandable liner hangers offer many novel features not available or applicable to conventional liner hangers. These features include radial geometry and a hanger / packer body construction with no moving parts. The primary benefits of this system are superior seal, improved installation reliability, and a significant reduction in time required to complete the installation and to resume drilling operations. These benefits and others derived from the features listed above will be discussed in detail in this paper including results from a recent case history in the Mossy Grove field of East Texas.IntroductionHistorically, many problems have been associated with the installation of a liner in oil and gas wells. As wells became more complex and tortuous due to drilling technology innovations, it became apparent that liner systems needed the ability to push, wash, and rotate to get the liner to the required setting depth. This has been accomplished with most modern types of liner hangers and setting tools to some degree, but at the expense of reliability.Conventional liner tops are prone to failure and an informal study performed in 1999 among operators in the Gulf of Mexico highlighted several problems associated with liner tops during the 18 months prior to the survey1(Fig. 1). Prevalent among the failure modes were:Liner top integrity - lap squeezesPacker/hanger/centralization issues - preset, or failure to setShoe integrity - shoe squeezesThese results confirm earlier studies that identified the effort and expense that operators required to ensure liner top hydraulic integrity.2 Typical methods of achieving this integrity include:Multiple liner top squeezes after failed primary cementingOne or more "second trip" liner top isolation packers installed to ensure liner top hydraulic integrityTack and squeeze liner setting technique (tacking the shoe with cement and then intentionally squeezing the liner top without attempting to cover the liner top during the primary cementing job)Many failures are caused by the design of very complex liner hangers. Conventional hanger/packer slips and cones provide a lodging place for cuttings to build up. Two results of this build-up are increased equivalent circulating density (ECD) leading to lost circulation and preset of the hanger or packer mechanically as cuttings become wedged under the external components. Pipe movement during cementing operations is also limited with conventional designs, since the hangers are set prior to cementing the wells. This can lead to poor cementing practices and poor cementing results, especially at the shoe and the liner top, where cement assists with the hydraulic seal.Additional concerns arise when trying to work or ream the liner to setting depth in deviated holes where cuttings removal can be difficult. Both rotation and pump rates are limited with conventional equipment. Conventional "drill-in" liner hangers are set or released by applying a differential pressure across the hanger or setting tool. Running and rotation speeds are limited due to slip design and the use of conventional packer elements integral to these tools. This limits the ability to effectively clean the hole. Keywords: hanger packer, well integrity, liner hanger system, expandable liner hanger application, packer, zonal isolation, case history, texas, drill pipe, liner Subjects: Drilling Operations, Drilling Fluids and Materials, Drilling fluid management & disposal, Well Integrity, Zonal isolation This content is only available via PDF. 2004. Society of Petroleum Engineers You can access this article if you purchase or spend a download.
The need for models of soil organic matter (SOM) turnover is similar to the need for many models of environmental processes: they are used to better understand processes; extrapolate or interpolate experimental results in time, space and to different environmental conditions; and to investigate scenarios and hypotheses that are beyond the realm of experimental work. As a result of this, a wide variety of SOM models have been developed, differing in their formulation and purpose. There are a number of approaches to modelling SOM turnover including process-based multi-compartment models, models that consider each fresh addition of plant debris as a separate cohort that decays in a continuous way, and models that account for carbon and nitrogen transfers through various trophic levels in a soil food web. This chapter aims to give a broad overview of currently available SOM models, highlighting areas of model application, identifying strengths and weaknesses and future directions for model development. We focus on two of the most widely used SOM models, RothC and CENTURY, to provide detailed case studies of model formulation, development and application.
Abstract The lignocellulosic perennial grass Miscanthus has received considerable attention as a potential bioenergy crop over the last 25 years, but few commercial plantations exist globally. This is partly due to the uncertainty associated with claims that land‐use change ( LUC ) to Miscanthus will result in both commercially viable yields and net increases in carbon (C) storage. To simulate what the effects may be after LUC to Miscanthus , six process‐based models have been parameterized for Miscanthus and here we review how these models operate. This review provides an overview of the key Miscanthus soil organic matter models and then highlights what measurers can do to accelerate model development. Each model ( WIMOVAC , BioCro, Agro‐ IBIS , DAYCENT , DNDC and ECOSSE ) is capable of simulating biomass production and soil C dynamics based on specific site characteristics. Understanding the design of these models is important in model selection as well as being important for field researchers to collect the most relevant data to improve model performance. The rapid increase in models parameterized for Miscanthus is promising, but refinements and improvements are still required to ensure that model predictions are reliable and can be applied to spatial scales relevant for policy. Specific improvements, needed to ensure the models are applicable for a range of environmental conditions, come under two categories: (i) increased data generation and (ii) development of frameworks and databases to allow simulations of ranging scales. Research into nonfood bioenergy crops such as Miscanthus is relatively recent and this review highlights that there are still a number of knowledge gaps regarding Miscanthus specifically. For example, the low input requirements of Miscanthus make it particularly attractive as a bioenergy crop, but it is essential that we increase our understanding of the crop's nutrient remobilization and ability to host N‐fixing organisms to derive the most accurate simulations.
Methane is a powerful greenhouse gas and is estimated to be responsible for approximately one-fifth of man-made global warming. Per kilogram, it is 25 times more powerful than carbon dioxide over a 100-year time horizon -- and global warming is likely to enhance methane release from a number of sources. Current natural and man-made sources include many where methane-producing micro-organisms can thrive in anaerobic conditions, particularly ruminant livestock, rice cultivation, landfill, wastewater, wetlands and marine sediments. This timely and authoritative book provides the only comprehensive and balanced overview of our current knowledge of sources of methane and how these might be controlled to limit future climate change. It describes how methane is derived from the anaerobic metabolism of micro-organisms, whether in wetlands or rice fields, manure, landfill or wastewater, or the digestive systems of cattle and other ruminant animals. It highlights how sources of methane might themselves be affected by climate change. It is shown how numerous point sources of methane have the potential to be more easily addressed than sources of carbon dioxide and therefore contribute significantly to climate change mitigation in the 21st century.
Rice is one of the world's most important staple crops and a major source of agricultural methane emissions. Breeding strategies such as photosynthate allocation modification and biomass enhancement show potential, but their effectiveness is highly context dependent, shaped by water regimes and soil organic carbon levels. Cultivars effective under continuous flooding may fail, or even increase emissions, under optimized water regimes. This perspective argues for integrated strategies that combine cultivar improvement with water and organic matter management, microbiome regulation, and climate-resilient breeding to build climate-smart rice systems that ensure both yield stability and methane mitigation.
Many former estimates of regional scale C sequestration potential have made use of linear regressions based on long-term experimental data, whilst some have used dynamic soil organic matter (SOM) models linked to spatial databases. Few studies have compared the two methods. We present a case study in which the potential of different land management practices to sequester carbon in soil in arable land is estimated by different methods. Two dynamic SOM models were chosen for this study, RothC (a soil process model) and CENTURY (a whole ecosystem model with a SOM module). RothC and CENTURY are the two most widely used and validated SOM models worldwide. A Geographic Information System (GIS) containing soil, land use and climate lavers, was assembled for a case study in central Hungary. GIS interfaces were developed for the RothC and CENTURY models, thus linking them to the spatial datasets at the regional level. This allowed a comparison of estimates of the C sequestration potential of different land management practices obtained using the two models and using regression based approaches. Although estimates obtained by the different approaches were of the same order of magnitude, differences were observed. Some of the land management scenarios studied here showed sufficient C mitigation potential to meet Hungarian CO2 reduction commitments. For example, afforestation of 12% current arable land could sequester 0.042-0.092 Tg yr(-1) in the soil alone, or 0.285-0.588 Tg C yr(-1) in both soil and biomass; 1990 level CO2 emissions for the study area were 4.7 Tg C with a corresponding reduction commitment of 0.282 Tg C. It is not, however, suggested that this is the only, or the most favourable way, in which to meet the commitments.
